Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 210345 AFDCTP Area Forecast Discussion National Weather Service State College PA 1145 PM EDT Mon Mar 20 2017 .SYNOPSIS... A weakening cold front will pass through the region overnight. A stronger cold front will move through Tuesday night bringing sharply colder air for mid week. Temperatures will moderate toward the end of the week into the weekend. && .NEAR TERM /UNTIL 7 AM TUESDAY MORNING/... Regional radar still shows the remnants of an MCS diving SE through southern Ohio into WV and eastern KY. To the north rain showers are becoming a little better organized over Ontario and the lower Gr Lakes. The HRRR still brings a slug of rain into the region mainly between about 11PM and 4AM, keeping the areal coverage limited and the QPF on the low side. Showers will tend to dissipate toward morning leaving little more than spotty drizzle. Overall I knocked POPS down a bit to better match latest timing. Temps should be mild overnight, running in the 30s. The coldest air up north could lead to a rain/snow mix as the precipitation tapers off late. Little or now accumulation is expected. && .SHORT TERM /7 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... High pressure will begin to build in for Tuesday. Clouds will likely hang tough over the region for much if not all of the day, but temperatures should be able to rebound a bit and return to near or slightly above normal. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Secondary/arctic front drops SSE across the region later Tuesday night/Wednesday morning with much stronger cold advection in the upper boundary layer (thanks to nearly orthogonal NW-NNW flow of 25-35 kts to the isotherms in 925-850 mb layer). The base of the subsidence inversion will be quite low (only around 4 kft AGL) and the fetch over the upstream glakes will be relatively short. So, the chance for significant LES will be rather low. However, the shallow strato cu deck will reside within the favorable DGZ thermal ribbon of -12 to -18C, so light accums of snow (up to around an inch) should occur across parts of the NW mtns and Laurel Highlands with just flurries elsewhere. The coldest air we`ll likely see until sometime later next fall will occur Wednesday into Thursday. Daytime highs and overnight lows will be 12-15F below normal. Mins early Thursday will range from near 10F along the PA/NY border, to the lower 20s in the larger metro areas in the Lower Susq Valley as a nearly 1040 mb sfc high drifts overhead. Some lows in the upper single digits will be a good possibility in the perennial cold spots up north. After a partly to mostly sunny and still rather cold day Thursday (by late March standards), clouds will increase Thursday night into Friday as a warm front drifts NE across the commonwealth. Sfc temps, and temps aloft (850 mb) will be a few to several deg C above freezing, so any light precip that occurs with this front will be light. The Warm front will likely lift into New York State and the warm sector should expand NE cover the entire CWA Friday afternoon through most of Saturday with temps surging well into the 40s to around 50F Friday, then into the lower 50s (north) to lower 60s (south) on Saturday. Timing and location of the deep cold air and associated 1040+ sfc high over southeastern Canada will play a key role in the storm track of a southern stream wave that will be sheared east from the Mid Miss Valley late Saturday...through the Ohio River Valley...Central Appalachians and Mid Atl Coast Sunday through Monday. Pops for rain/showers will increase Saturday night through Sunday night, but capped them off in the likely range at this point. Shallow cold air could backdoor us from the NE later in the weekend per the continued/consistent trend of the 12Z EC and GEFS. This could lead to some precip type issues across northern PA at a minimum. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/...
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Low pressure entering the Ohio Valley this evening will track south of Pa late tonight, spreading rain showers and falling CIGS across the region. Latest HRRR and SREF probability charts suggest IFR conditions are possible between 10Z-14Z at JST/BFD, MVFR conditions are likely at UNV/AOO and perhaps no sig reductions at the lower elevations airfields of eastern Pa, including IPT/MDT/LNS. Any showers should push east of the region around 12Z, as the low pressure system passes off the east coast. However, residual low level moisture ascending the Allegheny Mountains could create lingering MVFR stratocu at BFD/JST into early afternoon. The arrival of high pressure and drier air should result in widespread VFR conditions by late in the day, even BFD/JST. Outlook... Wed-Thu...No sig wx expected. Fri-Sat...Showers/reduced CIGS possible, mainly BFD.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Dangelo/Ceru LONG TERM...Lambert/Steinbugl AVIATION...Fitzgerald

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